BIOS Files Explained
What they are, which systems need them, and where to put them.
What is a BIOS?
BIOS stands for Basic Input/Output System. It is firmware stored on a chip inside the original console hardware. Think of it as the console's brain.
When you turn on a PlayStation 1, before any game runs, the BIOS does several things:
- Initializes the hardware (sets up the CPU, memory, graphics chip)
- Shows the startup animation and sound
- Provides core system functions that games rely on
- Reads the disc and launches the game
Some emulators need this BIOS code to work correctly. Without it, the emulator does not know how to initialize the virtual hardware or provide the system functions games expect.
Why Do Some Emulators Need BIOS and Others Do Not?
It depends on how the original console was designed and how the emulator was written.
Simpler consoles (NES, SNES, Genesis) did not have complex BIOS chips. Games contained all the code needed to run. Emulators can handle everything without external BIOS files.
CD-based consoles (PlayStation, Saturn, Dreamcast) had sophisticated BIOS that handled disc access, memory cards, and system services. Games relied on these BIOS functions. Emulators need the BIOS to provide these functions.
Some emulators have HLE (High-Level Emulation) where developers recreated the BIOS functions in code. These emulators work without a BIOS but might be less accurate. Other emulators require the original BIOS for full accuracy.
Which Systems Need BIOS?
| Requirement | Systems |
|---|---|
| Required | PlayStation 1, PlayStation 2, Sega Saturn, Sega CD, TurboGrafx-CD, Nintendo Switch, Original Xbox |
| Optional | Sega Dreamcast, Nintendo DS, GameCube (for boot animation), Game Boy Advance, 3DO |
| Not Required | NES, SNES, N64, Genesis, Master System, Game Gear, Game Boy, GBC, GBA, PSP, Wii, Wii U, most arcade games |
Where to Put BIOS Files
RetroDeck
Or on SD card:
EmuDeck
Or on SD card:
Important Rules
- Most BIOS go directly in the bios folder. Do not create subfolders unless the table below specifically says to.
- File names are case-sensitive. If the table says
scph5501.bin, do not useSCPH5501.BIN. - Use the exact file names. Emulators look for specific names.
Systems That Do NOT Need BIOS
These systems work without any BIOS files. Just add your ROMs and play.
| System | Notes |
|---|---|
| Nintendo NES / Famicom | No BIOS needed. FDS games need disksys.rom. |
| Super Nintendo (SNES) | No BIOS needed. |
| Nintendo 64 | No BIOS needed. |
| Nintendo Wii | No BIOS needed. |
| Nintendo Wii U | Encryption keys needed, not traditional BIOS. |
| Game Boy / Game Boy Color | No BIOS needed. |
| Game Boy Advance | Optional. Adds boot logo animation. |
| Sega Genesis / Mega Drive | No BIOS needed. |
| Sega Master System | No BIOS needed. |
| Sega Game Gear | No BIOS needed. |
| PlayStation Portable (PSP) | No BIOS needed. |
| Neo Geo Pocket / Color | No BIOS needed. |
| Atari 2600 | No BIOS needed. |
Sony Systems
PlayStation 1
Required
PlayStation 1 requires BIOS to run games. You need at least one BIOS file matching your game region.
| Region | File Name | Placement |
|---|---|---|
| Japan | scph5500.bin |
Directly in bios folder |
| North America | scph5501.bin |
Directly in bios folder |
| Europe | scph5502.bin |
Directly in bios folder |
These are the most commonly used BIOS versions. Other versions (scph1001, scph7001, etc.) also work. The 5500/5501/5502 series is preferred for compatibility.
If you have games from different regions, add all three BIOS files. The emulator will use the correct one automatically.
PlayStation 2
Required
PlayStation 2 requires BIOS. PCSX2 (the PS2 emulator) needs a full BIOS set including ROM files.
| File | Description |
|---|---|
SCPH-70012_BIOS_V12_USA_200.BIN |
Main BIOS file (US example) |
SCPH-70012_BIOS_V12_USA_200.EROM |
Extended ROM (optional but recommended) |
SCPH-70012_BIOS_V12_USA_200.ROM1 |
ROM bank 1 (optional) |
SCPH-70012_BIOS_V12_USA_200.ROM2 |
ROM bank 2 (optional) |
The exact file names depend on which PS2 model the BIOS came from. Any PS2 BIOS works. Place all files directly in the bios folder.
European and Japanese BIOS follow the same pattern with different model numbers.
PlayStation 3
Required (Different Method)
PS3 does not use traditional BIOS files. Instead, you install firmware through the RPCS3 emulator itself.
- Download the PS3 firmware from Sony's official website
- Open RPCS3
- Go to File, Install Firmware
- Select the downloaded firmware file
This only needs to be done once.
PlayStation Portable (PSP)
Not Required
PPSSPP includes everything it needs. No BIOS required.
PlayStation Vita
Required (Different Method)
Like PS3, Vita requires firmware installed through the Vita3K emulator, not a BIOS file.
Sega Systems
Sega CD / Mega CD
Required
| Region | File Name |
|---|---|
| North America | bios_CD_U.bin |
| Europe | bios_CD_E.bin |
| Japan | bios_CD_J.bin |
Place directly in the bios folder.
Sega Saturn
Required
| Region | File Name |
|---|---|
| Japan | sega_101.bin |
| North America / Europe | mpr-17933.bin |
Place directly in the bios folder. Some emulators (Kronos core) need saturn_bios.bin in a kronos subfolder.
Sega Dreamcast
Optional
Dreamcast emulators have built-in HLE BIOS that works for most games. Adding the real BIOS improves compatibility and adds the boot animation.
| File Name | Placement |
|---|---|
dc_boot.bin |
In bios/dc/ subfolder |
dc_flash.bin |
In bios/dc/ subfolder (optional) |
Dreamcast is one of the few systems that needs a subfolder. Create a folder called dc inside your bios folder and put the Dreamcast BIOS files there.
Nintendo Systems
Nintendo DS
Optional
The melonDS emulator works without BIOS using HLE mode. Adding BIOS files enables DSi mode and improves compatibility.
| File Name | Description |
|---|---|
bios7.bin |
ARM7 BIOS |
bios9.bin |
ARM9 BIOS |
firmware.bin |
DS firmware |
Place directly in the bios folder. For DSi games, additional files are needed (dsi_bios7.bin, dsi_bios9.bin, dsi_firmware.bin, dsi_nand.bin).
Nintendo 3DS
Optional/Required
For encrypted ROM files, you need AES keys:
| File Name | Placement |
|---|---|
aes_keys.txt |
Depends on emulator (see Citra docs) |
Decrypted ROMs do not need keys. Most ROMs you find are already decrypted.
Nintendo Switch
Required
Switch emulation requires both encryption keys and firmware dumped from your own Switch console.
For Ryujinx:
| File | Placement |
|---|---|
prod.keys |
bios/ryujinx/keys/ |
| Firmware | Installed through Ryujinx menu |
For Yuzu (if still available):
| File | Placement |
|---|---|
prod.keys |
bios/yuzu/keys/ |
| Firmware files | bios/yuzu/firmware/ |
Nintendo GameCube
Optional
The BIOS only adds the GameCube boot animation. Games work without it.
| File Name | Notes |
|---|---|
IPL.bin |
Must be placed in region-specific folder |
See Dolphin documentation for exact folder structure by region.
Famicom Disk System
Required
FDS games (the disk add-on for Famicom/NES) require BIOS:
| File Name | Placement |
|---|---|
disksys.rom |
Directly in bios folder |
Other Systems
TurboGrafx-CD / PC Engine CD
Required
| File Name | Description |
|---|---|
syscard3.pce |
System Card 3.0 (most compatible) |
syscard2.pce |
System Card 2.0 |
syscard1.pce |
System Card 1.0 |
gexpress.pce |
Games Express card |
Place directly in bios folder. syscard3.pce works for most games.
Panasonic 3DO
Required
| File Name | Placement |
|---|---|
panafz1.bin |
Directly in bios folder |
Other 3DO BIOS versions (panafz10, goldstar, sanyo) also work.
Atari Lynx
Required
| File Name | Placement |
|---|---|
lynxboot.img |
Directly in bios folder |
Original Xbox
Required
| File Name | Description |
|---|---|
mcpx_1.0.bin |
MCPX Boot ROM |
Complex_4627v1.03.bin |
Flash ROM Image |
Xemu requires specific BIOS versions. See Xemu documentation for details.
BIOS Troubleshooting
Game Will Not Boot
- Verify the BIOS file exists in the correct location
- Check the file name matches exactly (case-sensitive)
- Make sure you have the correct region BIOS for your game
- Try a different BIOS version
Wrong File Names
If your BIOS files have different names, rename them to match what the emulator expects. For example, if you have SCPH5501.BIN but the emulator wants scph5501.bin, rename it.
Corrupt BIOS
If a BIOS file is corrupted or the wrong file, games will not work. You can verify BIOS files by checking their MD5 checksum against known good values (search online for the correct checksums).
RetroDeck BIOS Checker
RetroDeck includes a BIOS checker tool in the Configurator. It verifies that your BIOS files are present and correct.
Where to Find BIOS Files
BIOS files can be found from several sources:
RetroArch System Files
Internet Archive hosts collections of system files compatible with RetroArch cores. Search for "RetroArch System" on Archive.org to find complete BIOS packs organized by system.
TOSEC Firmware Collections
TOSEC (The Old School Emulation Center) catalogs firmware and BIOS files. Their firmware collections are available on Myrient and Internet Archive.
Individual System Archives
BIOS files for specific systems are often included in ROM collections on Myrient. Look in the system folders for BIOS or firmware subfolders.
After downloading, verify your BIOS files match known-good checksums. Many emulators will tell you if a BIOS file is incorrect or missing. RetroDeck's BIOS checker is particularly helpful for this.